1. Field of the Invention
The present invention relates to a method of transferring data to be recorded, a recording apparatus and a recording system, and more particularly to a method of transferring data to be recorded which is adaptable to a recording apparatus having a vertical-type recording head comprising recording elements arranged to record a plurality of colors and disposed in a direction in which nozzles of the recording head are disposed, and to a recording apparatus and a recording system having the foregoing recording head to record an image.
2. Related Background Art
In recent years, office automation equipment, such as personal computers, word processors and the like, has been widely used. To print out information input from the foregoing equipment, a variety of recording methods and recording apparatuses have been developed. Information to be printed out is in a trend of being formed into color images as the performance of the office automation equipment has been improved. Under the foregoing circumstance, low cost color recording apparatuses and recording apparatuses capable of performing both color-image recording and high speed black-image recording have been developed.
A method of transferring color data when a color recording operation is performed in a serial recording apparatus for recording data by scanning a recording head will now be described. In the main scanning direction (hereinafter called as a "raster direction") of the recording head, image information for each color for each raster or in line units collecting a plurality of rasters is transferred. That is, yellow, magenta, cyan and black image data for the same raster or the same line is transmitted/received, and then yellow, magenta, cyan and black image data for the next raster is transmitted/received.
Data is, in the foregoing case, usually transmitted/received in parallel by a Centronics Interface method. Although the present Centronics Interface method is a one-directional transmitting/receiving method from a host computer to the recording apparatus, a bidirectional Centronics Interface method has been established with which data can be transmitted/received bidirectionally.
Recording means of a color recording apparatus for recording images in a plurality of colors are generally disposed in a lateral direction such that respective recording colors are disposed in parallel in the raster direction. The lateral configuration method suffers from a problem in that the size of the recording apparatus in the raster direction is enlarged excessively, a problem in that the order of superimposing the recording colors when the recording head moves forward for recording data and that when the same moves back are inverted and, therefore, the color tone of the recorded image is displaced, and a problem in that colors are undesirably mixed with each other or bleeding takes place because next color recording liquid reaches before the previously recorded recording liquid is fixed.
To overcome the foregoing problems, a countermeasure is taken such that the boundary of images to be recorded in different colors is detected; if a boundary exists, then printing is performed in such a manner that intermittent pausing is performed or one dot in the boundary portion is omitted in printing, or if the boundary portion is a boundary from a black image, then the boundary with the black image is converted (PCBk converted) into a combination with another color image.
Another method may be employed in which the recording means for the respective colors are disposed in the sub-scanning direction (in the vertical direction) to prevent bleeding of an image in the boundary portion. With the foregoing method, the time taken to record dots in the different colors to be printed with the same raster is elongated, thus preventing bleeding of an image in the boundary portion. Since the respective colors are offset in the sub-scanning direction in the foregoing method, the order of superimposing recording liquids is not changed between the case where the recording head moves forward and the case where the recording head moves back. Thus, an advantage can be realized in that the color tone cannot be displaced if images are recorded in the two directions. As a result, heads of a type having the vertical configuration have been widely used.
The vertical-configuration recording head comprising the yellow, magenta, cyan and black recording devices, which are disposed in the sub-scanning direction, inevitably has a large size in the sub-scanning direction. Accordingly, a black recording device, which is required to be capable of recording images at high speed and which is used frequently to print characters, has a multiplicity of nozzles and the yellow, magenta and cyan recording devices, which are required to be capable of recording high quality images and which are not required to be capable of recording images at high speed as compared with the black recording device, has a small number of nozzles so that the specification, cost and size are balanced.
However, the vertical-configuration head has a bit map, in which image data is developed, and which has a memory area (hereinafter called as a "print buffer") that requires a significantly larger region as compared with that of a lateral-configuration head. The required print buffer area of a vertical-configuration head will now be described with reference to the drawings.
FIG. 1 is a diagram showing a print buffer area of a vertical-configuration head. A recording head 1708 having 24 recording devices for recording yellow, magenta and cyan images and 64 recording devices for recording black images. A gap corresponding to 8 devices (pixels) is formed between recording device groups for recording different color images. The recording devices for the respective colors are arranged in the main scanning direction in an order of yellow, magenta, cyan and black.
When the recording head 1708 having the recording devices for recording a yellow image records a yellow image from (n) raster to (n+23) raster, the recording devices for recording a magenta image record a range from (n+32) raster to (n+55) raster, the recording devices for recording a cyan image record a range from (n+64) raster to (n+87) raster, and the recording devices for recording a black image record a range from (n+96) raster to (n+159) raster.
Since recording pixel data for each color is, in raster units or line units, transferred from an external apparatus, such as a host computer, to the recording apparatus, start of the recording operation is inhibited until transference of yellow, magenta, cyan and black data to be recorded to at least (n+159) raster is completed and as well as development of black recording data to (n+159) raster is completed in the print buffer. Although the recording devices for recording a yellow image is able to record the same if development of the image signal in the print buffer from the (n) raster to the (n+23) raster is completed, the recording devices for recording a yellow image must have the recording information to the (n+159) raster. Thus, a memory corresponding to 160 rasters is required as shown in FIG. 1.
If the recording resolution of the recording apparatus is 360 DPI, the image to be recorded has a size of an A4 sheet and the number of pixels in one raster is 2,880 pixels, the 160 rasters require a memory capacity of 460,800 (=160 rasters.times.2,880 pixels) bits. Similarly, the recording devices for recording a magenta image requires 368,640 bits (=128 rasters.times.2,880 pixels), the recording devices for recording a cyan image requires 276,480 bits (=96 rasters.times.2,880 pixels) and the recording devices for recording a black image requires 184,320 bits (=64 rasters.times.2,880 pixels). As a result, the yellow, magenta, cyan and black recording devices require a total memory area of 1,290,240 bits.
The print buffer area, to which a reference is made during one recording scanning operation, for each of the yellow, magenta and cyan recording devices is 69,120 bits (=24 rasters.times.2,880 pixels), whereas that for the black recording devices is 184,320 bits (=64 raster.times.2,880 pixels). The recording devices for recording yellow, magenta, cyan and black images require a total print buffer area of 391,680 bits, which is smaller than the half of the foregoing required bits of 1,290,240 bits.
The recording devices for recording a black image, which must record black characters at high speed, has a large number of recording elements as compared with those of the yellow, magenta and cyan recording devices. In a case where a color image is printed, only 24 recording elements for black are used because only 24 yellow, magenta and cyan recording elements are provided. Thus, 24 yellow, magenta, cyan and black recording elements are used to print the image and the paper is moved for a distance corresponding to the 24 nozzles. The foregoing recording operation is repeated. Although any recording element group may be used because 64 nozzles are provided for the black recording device, recording elements farthest from the yellow, magenta and cyan image are usually used to prevent bleeding occurring between different color images.
Although all of the 64 nozzles for a black image can be used only when a black image is printed, frequency of use varies among nozzles because only 24 specific nozzles are used when a color image is printed. Since deterioration of the nozzle occurring due to the time lapse changes depending upon the frequency of use, difference in the density arises between an image recorded by the nozzles used frequently and that recorded by the nozzle which are not used frequently. Thus, a desired image quality cannot be obtained. If the life of any one of the nozzles is closed, the life of the recording head is closed. Therefore, the offset in the frequency of use shortens the life of the recording head.
Although the vertical-configuration of the heads allows the time for fixing an image to be maintained and therefore bleeding in the boundary region can be prevented, bleeding cannot be prevented completely. Therefore, another bleeding preventive means is required to improve the quality of the image.
As described above, the conventional recording apparatus comprising the vertical-configuration recording head requires a print buffer (a memory) having a large capacity. Thus, the overall cost cannot be reduced. Furthermore, the time required to start recording from start of transference of data to be recorded from a host computer can be elongated. Thus, the time required to complete the recording operation is elongated excessively.